For many semiconductor integrated circuits, a field-effect MOS transistor (MOSFET) is used. What is necessary to improve the performance of integrated circuits is to improve the performance of the MOSFET. Conventionally, improvements of the performance of the MOSFET are achieved by making devices small in size. However, the problem is that as the length of a gate becomes shorter, a source diffusion layer and a drain diffusion layer become closer to each other, a depletion layer formed by each diffusion layer expands into a large portion of a channel region beneath a gate insulating film, the dominance of a gate electrode weakens, and a threshold value decreases (Short channel effect). What is proposed as a way of solving the short channel effect is a Schottky-barrier field-effect transistor (SBMOSFET) shown in FIG. 11. According to the structure, instead of an impurity diffusion layer, metal electrodes (drain silicide 11 and source silicide 12) are used as a source or drain; a Schottky junction is formed between the metal electrodes and a substrate 1. Incidentally, the reference numeral 3 represents a gate insulating film, 4 a gate electrode, and 7 a sidewall. FIG. 12A shows an energy band of the surface of a substrate of N-type SBMOSFET with zero bias. FIG. 12B shows the results of applying a bias with the gate voltage Vg>0 and the drain voltage Vd>0. In this case, electrons are poured into the channel region from the source silicide 12 thanks to a tunnel and run toward the drain silicide 11. In the case of the SBMOSFET, the depletion layer that expands in the channel region is smaller than in a MOSFET that uses a diffusion layer. Therefore, the SBMOSFET has high immunity to the short channel effect.